1. Field of the Invention
The present invention relates to a microscope and an immersion objective lens used for observing a semiconductor wafer and a liquid crystal substrate.
2. Related Background Art
In manufacturing semiconductor circuit devices or liquid crystal display devices, observations on defects or foreign bodies in a circuit pattern formed on a semiconductor wafer or a liquid crystal substrate (which are generally called a “substrate”) have been carried out by a microscope. Here, a microscope in this specification is an optical microscope system combined with an automatic transfer mechanism. There are two kinds of objective lenses one of which is a dry type in which a gas such as air and the like is filled between an object to be observed and an objective lens of the microscope system, and the other is a immersion type in which a liquid is filled between an object to be observed and an objective lens of the microscope system. By the way, the observation using the microscope system is corresponding to an inspection for observing the state and cause of defects or foreign bodies detected by a pattern defect inspection system.
Recently, a device for observing a substrate with visible light and ultraviolet light has been proposed (for example, Japanese Patent Application Laid-Open No. 2001-118896). The device is also a dry type. On using ultraviolet light, since resolving power is proportional to the wavelength to be observed, the substrate can be observed with higher resolving power than on using visible light. In the device disclosed in Japanese Patent Application Laid-Open No. 2001-118896, by combining observation with low resolving power upon using visible light and that with high resolving power upon using ultraviolet light, a substrate can be effectively observed.
However, since the device described above uses ultraviolet light, the kind of light source and optical materials of the observation system including an objective lens are limited to expensive ones, so that manufacturing cost and running cost become excessively high. Moreover, in order to improve resolving power with the above-described device using ultraviolet light, wavelength of the illumination light must be further shortened, so that the light source becomes excessively costly and also has a problem of stability.